Carbohydrate Challenge Tests: Do You Need to Measure Methane?

Objective: Breath tests that measure hydrogen (H-2) have been judged reliable for the detection of lactose maldigestion (LM) and fructose malabsorption (FM). Recently, methane (CH4) testing has been advocated and measurement of CH4 in addition to H-2 has been shown to increase the diagnostic accuracy for LM. Purpose: This study was designed to consider the additional yield from CH4 measurement in patients tested for LM and FM. Methods: Patients reported for testing after an overnight fast, not smoking and with their prior evening meal carbohydrate restricted. After challenge with 50 g lactose or 25 g fructose in water, end-alveolar breath samples collected over a 4-hour duration were analyzed for H-2 and CH4. Diagnostic positivity was compared using a cutoff level of 20 ppm increase above fasting baseline for H-2 alone, which is consistent with consensus guidelines, versus H-2 plus twice CH4, which recognizes that CH4 consumes twice the hydrogen. Results: There were 406 LM performed in 93 men and 313 women. Of those tested, 124 (30%) had a positive test for H-2 and 139 (34%) had a positive test for H-2 + CH4 x 2. There were 178 FM tests performed in 31 men and 147 women. Of those tested, 17 (9%) had a positive test for H-2 and 42 (23%) had a positive test for H-2 + CH4 x 2. Conclusion: If H-2 alone was measured without additional CH4 analysis, 4% of patients with LM and 14% patients with FM would not have been identified.